DESCRIPTION

This module has two interfaces, one through color() and colored() and the
other through constants. It also offers the utility functions uncolor(),
colorstrip(), and colorvalid(), which have to be explicitly imported to be
used (see SYNOPSIS).

Supported Colors

Terminal emulators that support color divide into two types: ones that
support only eight colors, and ones that support sixteen. This module
provides both the ANSI escape codes for the "normal" colors, supported by
both types, as well as the additional colors supported by sixteen-color
emulators. These colors are referred to as ANSI colors 0 through 7
(normal) and 8 through 15.

Unfortunately, interpretation of colors 0 through 7 often depends on
whether the emulator supports eight colors or sixteen colors. Emulators
that only support eight colors (such as the Linux console) will display
colors 0 through 7 with normal brightness and ignore colors 8 through 15,
treating them the same as white. Emulators that support 16 colors, such
as gnome-terminal, normally display colors 0 through 7 as dim or darker
versions and colors 8 through 15 as normal brightness. On such emulators,
the "normal" white (color 7) usually is shown as pale grey, requiring
bright white (15) to be used to get a real white color. Bright black
usually is a dark grey color, although some terminals display it as pure
black. Some sixteen-color terminal emulators also treat normal yellow
(color 3) as orange or brown, and bright yellow (color 11) as yellow.

Following the normal convention of sixteen-color emulators, this module
provides a pair of attributes for each color. For every normal color (0
through 7), the corresponding bright color (8 through 15) is obtained by
prepending the string bright_
to the normal color name. For example,
red
is color 1 and bright_red
is color 9. The same applies for
background colors: on_red
is the normal color and on_bright_red
is
the bright color. Capitalize these strings for the constant interface.

There is unfortunately no way to know whether the current emulator
supports sixteen colors or not, which makes the choice of colors
difficult. The most conservative choice is to use only the regular
colors, which are at least displayed on all emulators. However, they will
appear dark in sixteen-color terminal emulators, including most common
emulators in UNIX X environments. If you know the display is one of those
emulators, you may wish to use the bright variants instead. Even better,
offer the user a way to configure the colors for a given application to
fit their terminal emulator.

Support for colors 8 through 15 (the bright_
variants) was added in
Term::ANSIColor 3.0.

Function Interface

The function interface uses attribute strings to describe the colors and
text attributes to assign to text. The recognized non-color attributes
are clear, reset, bold, dark, faint, underline, underscore, blink,
reverse, and concealed. Clear and reset (reset to default attributes),
dark and faint (dim and saturated), and underline and underscore are
equivalent, so use whichever is the most intuitive to you.

Note that not all attributes are supported by all terminal types, and some
terminals may not support any of these sequences. Dark and faint, blink,
and concealed in particular are frequently not implemented.

Attributes, once set, last until they are unset (by printing the attribute
clear
or reset). Be careful to do this, or otherwise your attribute
will last after your script is done running, and people get very annoyed
at having their prompt and typing changed to weird colors.

color(ATTR[, ATTR ...])

color() takes any number of strings as arguments and considers them to be
space-separated lists of attributes. It then forms and returns the escape
sequence to set those attributes. It doesn't print it out, just returns
it, so you'll have to print it yourself if you want to. This is so that
you can save it as a string, pass it to something else, send it to a file
handle, or do anything else with it that you might care to. color()
throws an exception if given an invalid attribute.

colored(STRING, ATTRIBUTES)

colored(ATTR-REF, STRING[, STRING...])

As an aid in resetting colors, colored() takes a scalar as the first
argument and any number of attribute strings as the second argument and
returns the scalar wrapped in escape codes so that the attributes will be
set as requested before the string and reset to normal after the string.
Alternately, you can pass a reference to an array as the first argument,
and then the contents of that array will be taken as attributes and color
codes and the remainder of the arguments as text to colorize.

Normally, colored() just puts attribute codes at the beginning and end of
the string, but if you set $Term::ANSIColor::EACHLINE to some string, that
string will be considered the line delimiter and the attribute will be set
at the beginning of each line of the passed string and reset at the end of
each line. This is often desirable if the output contains newlines and
you're using background colors, since a background color that persists
across a newline is often interpreted by the terminal as providing the
default background color for the next line. Programs like pagers can also
be confused by attributes that span lines. Normally you'll want to set
$Term::ANSIColor::EACHLINE to "\n"
to use this feature.

uncolor(ESCAPE)

uncolor() performs the opposite translation as color(), turning escape
sequences into a list of strings corresponding to the attributes being set
by those sequences.

colorstrip(STRING[, STRING ...])

colorstrip() removes all color escape sequences from the provided strings,
returning the modified strings separately in array context or joined
together in scalar context. Its arguments are not modified.

colorvalid(ATTR[, ATTR ...])

colorvalid() takes attribute strings the same as color() and returns true
if all attributes are known and false otherwise.

Constant Interface

Alternately, if you import :constants
, you can use the following
constants directly:

CLEARRESETBOLDDARK

FAINTUNDERLINEUNDERSCOREBLINK

REVERSECONCEALED

BLACKREDGREENYELLOW

BLUEMAGENTACYANWHITE

BRIGHT_BLACKBRIGHT_REDBRIGHT_GREENBRIGHT_YELLOW

BRIGHT_BLUEBRIGHT_MAGENTABRIGHT_CYANBRIGHT_WHITE

ON_BLACKON_REDON_GREENON_YELLOW

ON_BLUEON_MAGENTAON_CYANON_WHITE

ON_BRIGHT_BLACKON_BRIGHT_REDON_BRIGHT_GREENON_BRIGHT_YELLOW

ON_BRIGHT_BLUEON_BRIGHT_MAGENTAON_BRIGHT_CYANON_BRIGHT_WHITE

These are the same as color('attribute') and can be used if you prefer
typing:

(Note that the newline is kept separate to avoid confusing the terminal as
described above since a background color is being used.)

When using the constants, if you don't want to have to remember to add the
,RESET
at the end of each print line, you can set
$Term::ANSIColor::AUTORESET to a true value. Then, the display mode will
automatically be reset if there is no comma after the constant. In other
words, with that variable set:

will not. If you are using background colors, you will probably want to
print the newline with a separate print statement to avoid confusing the
terminal.

The subroutine interface has the advantage over the constants interface in
that only two subroutines are exported into your namespace, versus
thirty-eight in the constants interface. On the flip side, the constants
interface has the advantage of better compile time error checking, since
misspelled names of colors or attributes in calls to color() and colored()
won't be caught until runtime whereas misspelled names of constants will
be caught at compile time. So, pollute your namespace with almost two
dozen subroutines that you may not even use that often, or risk a silly
bug by mistyping an attribute. Your choice, TMTOWTDI after all.

The Color Stack

As of Term::ANSIColor 2.0, you can import :pushpop
and maintain a stack
of colors using PUSHCOLOR, POPCOLOR, and LOCALCOLOR. PUSHCOLOR takes the
attribute string that starts its argument and pushes it onto a stack of
attributes. POPCOLOR removes the top of the stack and restores the
previous attributes set by the argument of a prior PUSHCOLOR. LOCALCOLOR
surrounds its argument in a PUSHCOLOR and POPCOLOR so that the color
resets afterward.

When using PUSHCOLOR, POPCOLOR, and LOCALCOLOR, it's particularly
important to not put commas between the constants.

will not, and a subsequent pop won't restore the correct attributes.
PUSHCOLOR pushes the attributes set by its argument, which is normally a
string of color constants. It can't ask the terminal what the current
attributes are.

DIAGNOSTICS

Bad escape sequence %s

(F) You passed an invalid ANSI escape sequence to uncolor().

Bareword "%s" not allowed while "strict subs" in use

(F) You probably mistyped a constant color name such as:

$Foobar = FOOBAR . "This line should be blue\n";

or:

@Foobar = FOOBAR,"This line should be blue\n";

This will only show up under use strict (another good reason to run under
use strict).

Invalid attribute name %s

(F) You passed an invalid attribute name to either color() or colored().

Generating this fatal compile error is one of the main advantages of using
the constants interface, since you'll immediately know if you mistype a
color name.

No name for escape sequence %s

(F) The ANSI escape sequence passed to uncolor() contains escapes which
aren't recognized and can't be translated to names.

ENVIRONMENT

ANSI_COLORS_DISABLED

If this environment variable is set, all of the functions defined by this
module (color(), colored(), and all of the constants not previously used
in the program) will not output any escape sequences and instead will just
return the empty string or pass through the original text as appropriate.
This is intended to support easy use of scripts using this module on
platforms that don't support ANSI escape sequences.

For it to have its proper effect, this environment variable must be set
before any color constants are used in the program.

RESTRICTIONS

It would be nice if one could leave off the commas around the constants
entirely and just say:

print BOLD BLUE ON_WHITE "Text\n" RESET;

but the syntax of Perl doesn't allow this. You need a comma after the
string. (Of course, you may consider it a bug that commas between all the
constants aren't required, in which case you may feel free to insert
commas unless you're using $Term::ANSIColor::AUTORESET or
PUSHCOLOR/POPCOLOR.)

For easier debugging, you may prefer to always use the commas when not
setting $Term::ANSIColor::AUTORESET or PUSHCOLOR/POPCOLOR so that you'll
get a fatal compile error rather than a warning.

NOTES

The codes generated by this module are standard terminal control codes,
complying with ECMA-048 and ISO 6429 (generally referred to as "ANSI
color" for the color codes). The non-color control codes (bold, dark,
italic, underline, and reverse) are part of the earlier ANSI X3.64
standard for control sequences for video terminals and peripherals.

Note that not all displays are ISO 6429-compliant, or even X3.64-compliant
(or are even attempting to be so). This module will not work as expected
on displays that do not honor these escape sequences, such as cmd.exe,
4nt.exe, and command.com under either Windows NT or Windows 2000. They
may just be ignored, or they may display as an ESC character followed by
some apparent garbage.

Jean Delvare provided the following table of different common terminal
emulators and their support for the various attributes and others have
helped me flesh it out:

Windows is Windows telnet, Cygwin SSH is the OpenSSH implementation under
Cygwin on Windows NT, and Mac Terminal is the Terminal application in Mac
OS X. Where the entry is other than yes or no, that emulator displays the
given attribute as something else instead. Note that on an aixterm, clear
doesn't reset colors; you have to explicitly set the colors back to what
you want. More entries in this table are welcome.

Note that codes 3 (italic), 6 (rapid blink), and 9 (strike-through) are
specified in ANSI X3.64 and ECMA-048 but are not commonly supported by
most displays and emulators and therefore aren't supported by this module
at the present time. ECMA-048 also specifies a large number of other
attributes, including a sequence of attributes for font changes, Fraktur
characters, double-underlining, framing, circling, and overlining. As
none of these attributes are widely supported or useful, they also aren't
currently supported by this module.

SEE ALSO

ISO 6429 is available from ISO for a charge; the author of this module
does not own a copy of it. Since the source material for ISO 6429 was
ECMA-048 and the latter is available for free, there seems little reason
to obtain the ISO standard.

AUTHORS

Original idea (using constants) by Zenin, reimplemented using subs by Russ
Allbery <rra@stanford.edu>, and then combined with the original idea by
Russ with input from Zenin. Russ Allbery now maintains this module.

COPYRIGHT AND LICENSE

Copyright 1996, 1997, 1998, 2000, 2001, 2002, 2005, 2006, 2008, 2009, 2010
Russ Allbery <rra@stanford.edu> and Zenin. This program is free software;
you may redistribute it and/or modify it under the same terms as Perl
itself.

PUSHCOLOR, POPCOLOR, and LOCALCOLOR were contributed by openmethods.com
voice solutions.